Hitachi Metals, Ltd.

Honda Motor Co., Ltd.

Katsuhiko Ohishi

Toshihiro Uehara

Takehiro Ohno

Kunichika Kubota

Akihiro Toji

Takahiko Kamimura

Kenji Yokoyama

Kenta Imazeki

Yuuichi Hadano

Ichiro Kishigami

The invention provides a maraging steel production method in which an oxide is added during an Mg oxide formation step, the production method including: the Mg oxide formation step in which Mg is added to molten steel and MgO is formed in the molten steel, during primary melting; a consumable electrode production step in which, after the Mg oxide formation step, the molten steel is solidified and a consumable electrode having residual MgO is obtained; and a vacuum arc re-melting step in which the consumable electrode is used and vacuum arc re-melting is performed.

Production method for maraging steel and production method for maraging steel consumable electrode

Provided is a maraging steel strip which has such a composition that can reduce the content of TiN acting as the starting point of fatigue fracture in a high-cycle region, and the bending fatigue strength of which has been improved by the precipitation hardening effect yielded by precipitating coherent nitrides in the nitrided structure. A maraging steel strip produced by nitriding a managing steel which contains by mass, C: 0.01% or less, Si: 0.1% or less, Mn: 0.1% or less, P: 0.01% or less, S: 0.005% or less, Ni: 8.0 to 22.0%, Cr: 0.1 to 8.0%, Mo: 2.0 to 10.0%, Co: 2.0 to 20.0%, Ti: 0.1% or less, Al: 2.5% or less, N: 0.03% or less, and O: 0.005% or less, with the balance being Fe and unavoidable impurities, wherein Baker-Nutting orientation relationship with an orientation difference within 10&#xb0; exists between the Cr nitride precipitated in the nitrided layer and the matrix martensite.

Maraging steel strip

To provide an inexpensive heat-resisting steel for engine valves by causing Fe-based heat-resisting steel to exhibit high temperature strength not inferior to that of Ni-based heat-resisting steel. A heat-resisting steel for engine valves excellent in high temperature strength containing, in % by mass, C: 0.20 to 0.50%, Si: 1.0% or less, Mn: 5.0% or less, P: 0.1 to 0.5%, Ni: 8.0 to 15.0%, Cr: 16.0 to 25.0%, Mo: 2.0 to 5.0%, Cu: 0.5% or less, Nb: 1.0% or less (including 0%), W: 8.0% or less (including 0%), N: 0.02 to 0.2%, B: 0.01% or less, and remnants of Fe and impurities, wherein the heat-resisting steel for engine valves satisfies formulae below:442P(%)+12Mo(%)+5W(%)+7Nb(%)+328N(%)+171&#x2267;300&#x2003;&#x2003;Formula (1)&#x2212;38.13P(%)+1.06Mo(%)+0.13W(%)+9.64Nb(%)+13.52N(%)+4.83&#x2267;0.12&#x2003;&#x2003;Formula (2).

Heat-resisting steel for engine valves excellent in high temperature strength

To provide an inexpensive heat-resisting steel for engine valves by causing Fe-based heat-resisting steel to exhibit high temperature strength not inferior to that of Ni-based heat-resisting steel. A heat-resisting steel for engine valves excellent in high temperature strength containing, in % by mass, C: 0.20 to 0.50%, Si: 1.0% or less, Mn: 5.0% or less, P: 0.1 to 0.5%, Ni: 8.0 to 15.0%, Cr: 16.0 to 25.0%, Mo: 2.0% or less (including 0%), Cu: 0.5% or less, Nb: 1.0% or less (including 0%), W: 2.0% or less (including 0%), N: 0.02 to 0.30%, B: 0.01% or less, and remnants of Fe and impurities, wherein the heat-resisting steel for engine valves satisfies formulae below:156.42P(%)+0.91Mo(%)+0.73W(%)&#x2212;12.27Nb(%)+220.96N(%)+120.59&#x2267;170&#x2003;&#x2003;Formula (1)13.70P(%)&#x2212;6.97Mo(%)&#x2212;4.32W(%)&#x2212;3.29Nb(%)+119.10N(%)+27.75&#x2267;25&#x2003;&#x2003;Formula (2).

Heat-resisting steel for engine valves excellent in high-temperature strength

A piston ring material is provided which retains excellent mechanical properties and processability, which are required of piston ring materials, and has wearing resistance and scuffing resistance, which are sliding properties required of piston rings. The piston ring material, which is for use in internal combustion engines, contains, in terms of mass %, 0.3-0.8% carbon, 0.1-3.0% silicon, 0.1-3.0% manganese, 0.01-0.3% sulfur, 0.1-2.0% chromium, and 0.05-2.0% the sum of titanium and/or zirconium, with the remainder being iron and incidental impurities. The titanium and/or zirconium contained in the piston ring material and the sulfur contained therein satisfy the following relationship. [Ti (%)+&#xbd;Zr (%)]/S (%)&#x2266;5.0 Preferably, the material may contain one or more members selected from up to 1.0% copper, less than 3.0% molybdenum, up to 1.0% aluminum, and less than 2.0% nickel, in terms of mass %.

Piston ring material for internal combustion engine

An alloy to be surface-coated, which can keep excellent hardness of 58HRC or above even when the amount of an alloying element added is reduced or even when the alloy is heated to a temperature of as high as 400 to 500&#xb0; C.; and sliding members produced by forming a hard film on the surface of the alloy. An alloy to be surface-coated, the surface of which is to be covered with a hard film, which alloy contains by mass C: 0.5 to 1.2%, Si: 2.0% or below, Mn: 1.0% or below, Cr: 5.0 to 14.0%, Mo+1/2 W: 0.5 to 5.0%, and N: more than 0.015 to 0.1% with the balance being Fe and impurities, preferably such an alloy which contains by mass C: 0.6 to 0.85%, Si: 0.1 to 1.5%, Mn: 0.2 to 0.8%, Cr: 7.0 to 11.0%, Mo+1/2 W: 1.0 to 4.0%, and N: 0.04 to 0.08%.

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Yasugi, Japan

Katsuhiko Ohishi